U.S. Pat. No. 3,780,011 to Pullukat, et al. discloses the use of catalysts containing chromium, titanium, boron, or vanadium. Also known is the use of catalysts containing antimony and vanadium. The above prior art neither discloses nor suggests the catalytic composition of the present invention which contains at least one element selected from the group consisting of an alkali metal, zinc, cadmium, arsenic, copper, cerium, thorium, iron, tin and manganese in addition to vanadium and boron.
U.S. Pat. No. 4,003,978 to Shiraishi, et al. discloses use of catalysts containing chromium, at least one element selected from the group consisting of tin, antimony, vanadium, cobalt, silver, zinc, nickel, titanium, molybdenum, tungsten, phosphorus, boron, germanium, and zirconium; U.S. Pat. No. 3,554,931 to Brown, et al. discloses use of catalysts containing antimony, vanadium, and optionally at least one element selected from the group consisting of tin, titanium, chromium, manganese, iron, cobalt, nickel, copper, zinc, molybdenum, cadmium, tungsten or thorium; U.S. Pat. No. 3,579,574 to Teunis van der Meer discloses use of a catalyst containing antimony and vanadium or vanadium, antimony and at least one element selected from the group consisting of iron, manganese, chromium, cobalt, nickel, copper, zinc, cadmium, tungsten and thorium; U.S. Pat. No. 4,010,238 to Shiraishi, et al. discloses use of catalysts containing vanadium and at least one element selected from the group consisting of copper, zinc, tin, lead, titanium, phosphorus, chromium, iron, cobalt and nickel; and U.S. Pat. No. 3,424,781 to Capp, et al. discloses use of catalysts containing antimony, chromium and vanadium. Nowhere do any of these patents suggest that arsenic may be successfully incorporated as an essential catalytic component when antimony, zinc or chromium is present.
U.S. Pat. No. 3,704,317 to Yamashita, et al. discloses use of catalysts containing vanadium and one or more of the secondary elements lithium, boron, silicon, chromium, iron, nickel, zinc, zirconium, niobium, rubidium, rhodium, tantalum and bismuth. In the Specific Embodiments portion of this reference is exemplified use of catalysts containing vanadium and single promoters of lithium, chromium, rhodium, zinc, boron, zirconium, bismuth, nickel, niobium, palladium and tungsten. Nowhere does Yamashita, et al. show the effectiveness of combining, for example, zinc and niobium. There is nothing in the patent to lead one to specifically select boron, zinc, tungsten and niobium from the large class of listed metals stated to have catalytic value.
U.S. Pat. No. 3,544,616 to Grasselli, et al. discloses use of a catalyst containing an essential catalytic components uranium and arsenic promoted by molybdenum, boron, vanadium, tin, nickel, bismuth, chromium, iron, manganese, zinc, tungsten, antimony, cerium, cobalt or rhenium. Uranium, an integral component in the Grasselli, et al. catalyst, is nowhere listed among the ingredients of the claimed catalyst composition of the present invention.
U.S. Pat. No. 3,855,318 to Nakajima, et al. discloses use of catalysts containing vanadium, iron, and at least one oxide of magnesium, titanium, manganese, beryllium or boron. In accordance with the present invention, boron and iron are not combined as catalytic ingredients. One would not be led to delete the iron from the catalyst of Nakajima with an expectation of success.
U.S. Pat. No. 3,907,919 to Ching-Tsan Lo discloses a catalyst containing a vanadate of Group IVA and/or VA metals promoted by compounds of Group VB, VIB or Group VIII of the Periodic Table. In view of the vast list of possible catalytic ingredients described in the Lo patent, one would not be led to the specifically defined catalyst composition of the present invention.
U.S. Pat. No. 2,954,385 to Burney, et al. discloses use of catalysts containing vanadium and at least one element selected from the group consisting of phosphorus, aluminum, titanium, iron, cobalt, zinc, copper, nickel, magnesium, manganese, silver, antimony and bismuth. In accordance with the preferred procedure of the present invention, when antimony and zinc are present as catalytic components arsenic must also be present. British Pat. No. 1,011,678 to Mihail discloses use of catalysts containing vanadium, boron and at least one of cerium, uranium and tin. In accordance with the present invention, where boron is present as a catalytic component cerium and tin may not be present.
U.S. Pat. No. 4,075,231 to Dolhyj, et al. discloses the preparation of phthalic anhydride from orthoxylene using coated catalysts containing Fe, Cr, Ni, Co, Mn, Cu, Ag, Bi, Zn, Mo, W or mixture thereof, boron, antimony, or mixture thereof, vanadium and oxygen. U.S. Pat. No. 4,076,731 to Dolhyj, et al. discloses the preparation of phthalic anhydride using a coated catalyst containing vanadium, oxygen, and boron, antimony, or mixture thereof. The catalyst composition of the present invention cannot be constructed from a reading of these patents.